Recently, various access network technologies that may accept various multimedia services, such as a rapidly increasing Internet protocol television (IPTV) and video on demand (VOD) service, and Internet service, applications, and the like, and that may provide a quality of service-guaranteed broadband service, have been developed. An access network may be constructed as a switching network based on an active device requiring a power supply or may be constructed as a passive sharing network based on a passive device. Generally, the switching network is a network that divides and classifies a broadcast domain of downstream data into a predetermined output interface and forwards the same, based on an active device, such as a router and a switch. The passive sharing network is a network where the all data is broadcasted downstream. However, although the switching network based on the active device is used, all inputted data is forwarded to all output ports, since the broadcast domain is not divided in a network where a device such as a dummy hub, several digital subscriber line access multiplexers (DSLAMs) that have no ability to interpret an Internet group management protocol (IGMP), and the like. Accordingly, a network under the described environment may also be the passive sharing network.
As an example, among current access network technologies for providing a broadband service, a passive optical network technology (PON) that has economical advantage by using a simple passive device has been dramatically developed.
FIG. 1 is a diagram illustrating an example of a conventional passive access network.
Referring to FIG. 1, a PON is a point-to-multipoint passive network where a single optical line terminal (OLT) 10 accesses multi-optical network terminals (ONT) 30. That is, the single OLT 10 accesses the multiple ONTs 30 by using a plurality of passive splitters 50, thereby sharing a bandwidth of a broad network. Accordingly, a cost for supplying a power may not be expended since a passive device is only used between the OLT 10 and the ONT 30, and a reliability of a network operation may increase since an electronic component is not used. Also, an upgrade of the network or establishment of additional networking may be simple, and an installation space in a central office (CO) or in a point of presence (POP) may be reduced since a plurality of subscribers may be accepted by installing the single OLT 10.
A multicast may simultaneously transmit a single broadcasting stream data to a plurality of subscribers included in the same group. In other words, the single broadcasting stream is transmitted to a multicast router 90 from a server 70 operated by an broadcasting operator in a similar manner as a conventional broadcasting scheme, and copied contents is transmitted, from the multicast router 90, only to subscribers in a group including a viewer requesting the broadcasting stream, namely, only to a corresponding user terminals, by using an IGMP, and thus, the bandwidth is effectively used. When a multicast packet is received, the multicast router 90 may perform flooding of the multicast packet according to a multicasting forward entry that is generated by a multicast routing protocol. Here, the flooding is transmitting a single packet received from an upper node to other terminals connected to the multicast router 90 or advertising corrected routing information corresponding to every neighbor node in a large-scaled network.
The IGMP is constituted by a membership query message and a membership report message, and multicast routers 90 may transmit a general query to a destination, “224.0.0.1”, to ascertain a group of subscribers accessing the corresponding router. The subscribers may transmit the membership report message in response to the membership query message received from the multicast router 90, thereby responding to the corresponding query. Also, a group-specific query or a group-and-source-specific query is a query to inquire about whether another participant exists in the corresponding group, when the multicast router 90 receives an IGMP leave report with respect to a specific group. An IGMP snooping protocol may sense an IGMP protocol packet exchanged between the multicast router 90 and the terminal, and may enable the multicast router 90 to recognize an adjacent port based on a media access control (MAC) address of each port.
In the access network, a plurality of users share the same network resource. Particularly, when the passive device is used, downstream data is broadcasted to all users, without being switched. Accordingly, when a multicast push-type service is provided based on the passive access network, every subscriber accessing the same service node may receive both a requested broadcasting program and unrequested broadcasting program. That is, when a subscriber views a specific broadcasting program, other subscribers accessing the same service node may receive the corresponding program. However, the conventional IGMP group management method has a problem where only a group that explicitly joins by directly sending a join message is recognized. Accordingly, although a user's terminal receives a broadcasting program requested by another user, the user may not view the corresponding program immediately. Also, there is an inefficiency that an explicit IGMP join report is always transmitted to the multicast router to view the broadcasting program currently received, and there is a problem that the user experiences a delay time where the procedure is performed, to view the requested program.